Diapositiva 1

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http//panda.unm.edu/fields/partonorbital.html
G.Bunce (RBRC) B. Hannafious (NMSU) A.Miller
(TRIUMF) D.Hasch(DESY)

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The total intrinsic k- carried by quarks

• Extraction of the Sivers function
• What do we learn from it?
• k- and orbital angular momentum
• Orbiting quarks ?

?
Mauro Anselmino, Parton Orbital Angular Momentum,
RBRC-UNM Workshop, Albuquerque, 24-26/02/2006
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predictions for JLab, proton target
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k- and orbital angular momentum (case of 2
quarks)
Does
?
imply
It depends on space distribution to be
continued
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Sivers Effect
Douglas Fields University of New Mexico/RBRC

• Recently, at the RBRC Single Spin Workshop, Denis
  Sivers gave a nice conceptual (no twist-anything)
  picture of how orbital angular momentum could
  cause a single transverse spin asymmetry.
• Quantum Fan description (top view spin down)

No Sivers Effect without interaction with
absorber Higher twist effect
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Werner Vogelsang RBRC and BNL Nuclear Theory
fragm., 0.25 GeV2
GRV, GRSV, KKP
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Parton picture Longitudinal and transverse
variables
H.Avakian
long before
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Extraction of GPD H from ALU moment
cLU
ALU/cLU
epg

x(F1F2)H kF2E
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2ltQ2lt2.4 GeV

• Redblue points correspond to projected ALU
  uncorrected for p0 (bin by bin)
• H stands for the ratio of the ALU and prefactor
  calculated for all events in a bin (averaged over
  f)
• Curves are for a simple model for CFF H (blue)
  and H(red)

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Exclusive r0 production on transverse target
2D -(Im(AB))/p

AUT -
A2(1-x2) - B2(x2t/4m2) - Re(AB)2x2
A 2Hu Hd B 2Eu Ed
r0
A Hu - Hd B Eu - Ed
r
r0
Eu, Ed needed for angular momentum sum rule.
(60 days)
K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001
Asymmetry is a more appropriate observable for
GPD studies at JLab energies as possible
corrections to the cross section are expected to
cancel
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Target SSA measurements at CLAS
ep?epX
W2gt4 GeV2
CLAS PRELIMINARY
p1sinfp2sin2f
Q2gt1.1 GeV2
ylt0.85
0.4ltzlt0.7
MXgt1.4 GeV
PTlt1 GeV
0.12ltxlt0.48
p1 0.0590.010 p2-0.0410.010
p1-0.0420.015 p2-0.0520.016
p10.0820.018 p20.0120.019

• Significant SSA measured for pions with
  longitudinally polarized target
• Complete azimuthal coverage crucial for
  separation of sinf, sin2f moments

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COMPASS plans to measure GPDs
Jean-Marc Le Goff DAPNIA/CEA-Saclay 24 Feb 2006,
Albuquerque workshop on Orbital Angular Momentum

• The COMPASS experiment
• GPDs at COMPASS
• now deep r production
• 2010 DVCS and HEMP

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Conclusions on rho

• SCHC ? R
• stot R ? sL
• when Q2 gt 2 ? R gt 1 accurate sL
• we have transv. target spin asym ? E/H
• important for Ji sum rule (?EH)
• exploratory measurement
• (no exclusivity, nuclear target)

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Additions to COMPASS setup
? ECal 1 or 2 ?? ? 12
Exclusivity at high energy dDM2
d(mpmp)2-mp2 gt 1 GeV2 need 0.25 GeV2 for
DM cut ? hermetic detector
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at 100 GeV
BCA
Q24?0.5 GeV2
x 0.05 0.02
Model 1 H(x,0,t) q(x) F(t)
Model 2
H(x,0,t) q(x) e t ltb?2gt q(x) /
xat

• assuming
• L 1.3 1032 cm-2 s-1
• 150 days
• efficiency25
• 2 bins shown out of 18
• 3 bins in xBj 0.05, 0.1, 0.2
• 6 bins in Q2 from 2 to 7 GeV2

f
f
BCA
x 0.10 0.03

f
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Outline
Feng Yuan RIKEN/BNL Research Center Brookhaven
National Laboratory

• Why naïve parton model fails for SSAs
• Two mechanisms Sivers and twist-3
• Unifying these two
• What we learn from SSA?
• Summary

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TMD Factorization

• When q? Q, a TMD factorization holds
• When q?À?QCD, all distributions and soft factor
  can be calculated from pQCD, by radiating a hard
  gluon

In the intermediate range QÀq?À?QCD 2 approaches
overlap and should give the same answer !!!
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Final Results

• P? dependence
• Which is valid for all P? range

Sivers function at low P?
Qiu-Sterman Twist-three
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Using Dijets to Measure the Gluon Sivers
Functions at STAR
Renee Fatemi Massachusetts Institute of
Technology February 28, 2005
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Jet 1
Sivers Effect in Dijets
Deviations from ? ? due to Partonic kT

• Gluon (U D) / 2
• Gluon 0
• Gluon D
• Gluon D vkT2 2.5

Maximal Effects at ?? 0.4-0.5. This region
experimentally available!
W.Vogelsang and D.Boer Phys Rev D 69 (2004)
094025
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Summary and Discussion

• STAR Collaboration is invested in studying all
  aspects of spin puzzle.
• Transverse running has high priority for STAR in
  2006.
• Recent developments in hardware, shielding and
  triggering should enable us to produce first
  statistically significant measurement of dijet ??
  asymmetry.

• Do we need to worry about Collins effects from
  first gluon scattered from polarized quark? How
  does this effect vary with cone size?
• If size of partonic kT is independent of hard
  scattering scale (jet pT) then shouldnt this
  asymmetry become smaller at higher jet pT?
• How will Sivers Functions be extracted from
  this asymmetry? What is the status of the
  necessary factorization theorems?
• Can we extract ?Lg from Sivers?

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Forward Particle Production and Transverse Single
Spin Asymmetries

• OUTLINE
• Transverse single spin effects in pp
  collisions at ?s200 GeV
• Towards understanding forward p0 cross sections
• Plans for the future

L.C. Bland Brookhaven National Laboratory RBRC
Workshop on Parton Orbital Angular
Momentum Albuquerque 25 February 2006
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AN(pT) from run3run5 at vs200 GeV
Uses online beam polarization values

• Combined statistics from run3 and run5 with
  xFgt0.4
• There is evidence that analyzing power at xFgt0.4
  decreases with increasing pT
• To do systematics study

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Plans for the Future

• STAR Forward Pion Detector upgrade (FPD)
  planned as an engineering test of the FMS during
  RHIC run 6
• STAR Forward Meson Spectrometer (FMS) planned
  for installation by RHIC run 7
• Disentangle the dynamical origins to transverse
  SSA in pp collisions via measurements of AN for
• jet-like events
• direct photon production

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Sample decays on FPD
H.A. Separate photons from p0?
With FPD module size and electronic dynamic
range, have gt95 probability of detecting second
photon from p0 decay.
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Outline
Yuji Goto (RIKEN/RBRC) SSA Measurements with
Primary Beam at J-PARC

• Introduction
• J-PARC
• spin physics with primary beam at J-PARC
• Drell-Yan experiment
• SSA measurements
• Summary

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SSA on Drell-Yan

• no final-state effect
• sensitive to Sivers effect at low qT qT ltlt Q

H.A. In the region of 0.2ltxlt0.4 should be able to
measure also the Mulders function measured at CLAS
integrated over qT
Sivers function fit from Vogelsang Yuan PRD
72, 054028 (2005).
(from Xiangdong Jis slide at J-PARC
hadron structure workshop at KEK, December, 2005)
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Summary

• For the spin physics program with primary beam at
  J-PARC, study group for the polarized proton
  acceleration and the physics experiment were
  formed, and discussions are underway
• Measurement of the orbital angular momentum
  component in the nucleon is one of the most
  important goal of the spin physics program at
  J-PARC
• Drell-Yan experiments are planned
• SSA measurements of Drell-Yan, pions, D-mesons,
  etc.
• gluon polarization at large-x, transversity, etc.
• Physics and detector studies are ongoing
• Collaboration with many groups in the world is
  very important

D-mesons from intrinsic charm ? no QCD applicable
(S.B.)